Abstract
The interaction of cyclodextrins (CDs) with lipid membrane was investigated in terms of the leakage of marker compound, calcein, entrapped in inner aqueous phase of liposome, and the time course of surface pressure of monolayer of lecithin or cholesterol in the presence of aqueous CD solutions. The surflace pressure of monolayer of lecithin spread on CD solution decreases in the order, α->β->γ-CD, while that of cholesterol lies in the order, β->γ->α-CD. The leakage of entrapped calcein lies in the order Di-O-methyl-β->α->β->Tri-O-methyl-β->γ-CD for the liposome composed of 83 molar percent egg yolk lecithin and 17 molar percent dihexadecylphosphate. While the leakage of calcein lies in the order Di-Omethyl-β->β->α->γ->Tri-O-methyl-β-CD for the liposome composed of equimolar mixture of egg yolk lecithin and cholesterol, and 17 molar percent dihexadecylphosphate. Judging from the above results, CD molecules recognize the lipid molecule in membrane by virtue of their cavity size for nonmethylated CD, and the cavity size and the hydrophobic character for methylated CDs. Then, they pull out the lipid molecules by forming the inclusion complex, resulting in the destruction of membrance structure.
